I think is a good idea that “PLUGIN” and “EXT MIDI” can be layeralbe just like sample!
Explain. I’ve not had any plugins installed since about version 2.0 but pretty sure you always could (and hopefully still can) load all associate samples, a plugin and MIDI Out as part of the same Instrument. Is this not the case?
Or do you mean multiple plugins within one instrument? Giving (for one example) easy access to split keyboard for Bass plus Pad from a different plugin each (plus much more, including easy instrument layerinig people ask for a lot of the time.) More I think about it the more obvious it is you mean this… 
Yes, I mean the ability to load more than one vst in the same instrument, just like in the sample zone! the same for ext midi, I want (would like) to play more than one keyboard at the same time with only one note track!
INSTRUMENT 01:
SAMPLE1 VOLUME PAN TRANSPOSE FINE …
SAMPLE2 …
SAMPLE3 …
…
VST1 VOLUME PAN BANK PATCH TRANSPOSE FINE …
VST2 …
VST3 …
…
MIDI OUT1 VOLUME PAN BANK PATCH TRANSPOSE FINE …
MIDI OUT2 …
MIDI OUT3 …
…
I hope I’m explained (sorry for my english), I’m from Cremona, Italy!!!
and also lo note, hi note, lo vel, hi vel! in this way you can create split, layer…